Evaluation Of Nitrogen Management Strategies For Impacts On Nitrate Leaching and Quality Of St. Augustinegrass Turfgrass.

Nitrogen (N) application is important for maintaining the aesthetic quality of turf. However, frequent arguments about the possible chances of water pollution through nitrate-nitrogen (NO₃-N) have focused attention on N application in turf. This research was conducted, over three years, at Citra, Florida to determine an environmentally friendly approach to N management in St. Augustinegrass. Ten fertilizer treatments were laid out in randomized complete-block design. Drainage lysimeters were installed to collect leachate and the leachates were analyzed for NO₃-N concentration. The NO₃-N leaching loads were similar among fertilizer treatments and also not different from the control (average 2.1 kg.ha^-1.yr^-1).   However, there was significant seasonal variation in leaching load. More than 90 percent of the total nitrate (6.3 kg.ha^-1) leached in three years, occurred in the first four months of the experiment, during turfgrass establishment. Thereafter, the seasonal loads were consistently lower (average 0.082 kg.ha^-1) and were not affected by fertilizer treatment. The quality of the grass was affected by fertilizer treatment and time of the year. Higher fertilizer rates resulted in greater turfgrass quality. Better quality was observed during the August-September period, however, the quality with all treatments declined with time over the three-year experimental period. The results indicated that fertilization is necessary to maintain the quality of the grass. Healthy turfgrass is effective at taking up N fertilizer and fertilization programs were not associated with NO₃-N leaching.  There were numerous fertilization strategies involving source and timing that resulted in acceptable turfgrass quality while minimizing the loss of N.